1. Field of the Invention
This invention relates generally to a circuit for regulating the supply of power to a load, and in particular, to a circuit that opens and closes a switch to automatically turn on and off a shunt regulator, depending on the power dissipated by the shunt regulator.
2. Description of the Related Art
Various types of protective circuits are well known in the art. For example, see U.S. Pat. No. 5,465,188 granted to Pryor et al. and U.S. Pat. No. 4,899,098 granted to Gariboldi.
Also well known is a circuit called "shunt regulator" that controls the voltage applied to a load by controlling the current flowing through a branch coupled in parallel to a power supply and an electrical load. For example, U.S. Pat. No. 5,444,358 granted to Delepaut describes a "regulator . . . [that] includes a branch circuit therein which in turn includes a series connection of at least a shunt switch . . . , said branch circuit being coupled in parallel with both a load and a power supply. Said power supply shunt regulator further includes current limitation means for generating an analog control signal that is applied to a control electrode of said shunt switch so as to limit the amount of current flowing through said shunt switch . . ." (col. 2, lines 10-29).
Delepaut further states that "the peak discharge current will clearly be limited to a fixed value dependent solely on the resistance of the current sensing resistor and a transfer function of the analog control signal realized by the current limitation means" (col. 2, lines 33-37). See also U.S. Pat. No. 4,390,829 granted to Jarrett for another example of a shunt regulator.